linux-kernel - Re: [PATCH 03/25] add dyn

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Date:	Sun, 03 Aug 2008 06:03:03 +0200
From:	Johannes Weiner <hannes@...urebad.de>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/25] add dyn_array support

Hi,

Yinghai Lu <yhlu.kernel@...il.com> writes:

> could have crazy big arrays and allocate them in bootmem at init stage.
> also also to allocate array according to size we need to use to avoid wasting
> memory
> use CONFIG_HAVE_DYN_ARRAY to enable it or not
>
> usage:
>
> |static struct irq_desc irq_desc_init __initdata = {
> |       .status = IRQ_DISABLED,
> |       .chip = &no_irq_chip,
> |       .handle_irq = handle_bad_irq,
> |       .depth = 1,
> |       .lock = __SPIN_LOCK_UNLOCKED(irq_desc->lock),
> |#ifdef CONFIG_SMP
> |       .affinity = CPU_MASK_ALL
> |#endif
> |};
> |
> |static void __init init_work(void *data)
> |{
> |       struct dyn_array *da = data;
> |       struct  irq_desc *desc;
> |       int i;
> |
> |       desc = *da->name;

Where *da->name might be NULL...

> |
> |       for (i = 0; i < *da->nr; i++)
> |               memcpy(&desc[i], &irq_desc_init, sizeof(struct irq_desc));

... boom.

> +void pre_alloc_dyn_array(void)
> +{
> +#ifdef CONFIG_HAVE_DYN_ARRAY
> +	unsigned long size, phys = 0;
> +	struct dyn_array **daa;
> +
> +	for (daa = __dyn_array_start ; daa < __dyn_array_end; daa++) {
> +		struct dyn_array *da = *daa;
> +
> +		size = da->size * (*da->nr);
> +		print_fn_descriptor_symbol("dyna_array %s ", da->name);
> +		printk(KERN_CONT "size:%#lx nr:%d align:%#lx",
> +			da->size, *da->nr, da->align);
> +		*da->name = __alloc_bootmem_nopanic(size, da->align, phys);

So, why is this _nopanic()?

> +		phys = virt_to_phys(*da->name);
> +		printk(KERN_CONT " ==> [%#lx - %#lx]\n", phys, phys + size);
> +
> +		if (da->init_work)
> +			da->init_work(da);
> +	}
> +#endif

	Hannes
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